Safety device

ABSTRACT

A safety device for an apparatus to be manipulated by an operator. The apparatus is connected via a supply line for a supply means to a supply means source. A handgrip is provided to be grasped by the operator for controlling the operation of the apparatus. An operating sensor is actuated by the operator and is connected to the control device. The operating sensor may be an electric proximity switch provided so that it is possible to shut off the apparatus when the operator ceases to actuate the operating sensor. The operating sensor, or at least one indiciator element of the operating sensor, is disposed on the hand of the operator, particularly integrated into a protective glove for the hand of the operator.

This is a continuation of application Ser. No. 123,424 filed Nov. 20,1987 Pat. No. 4,814,632.

FIELD OF THE INVENTION

The invention relates to a safety device for an apparatus used by anoperator, the apparatus to be used by an operator being connected to apower supply via a supply line, comprising a handgrip grasped orenfolded by the operator, where the operation of the apparatus ispreferably controllable from the power source, with a control device forthe control of the operation of the apparatus and with an operatingsensor disposed on the apparatus, which is actuated by the operator andpreferably connected with the control device via a cable, the operatingsensor being designed as an electronic proximity sensor, preferablyoperable contact-free, which is preferably actuated by a specialactuation element, particularly a foil, preferably aluminum, copper, amaterial of low magnetic retentivity with high initial permeability,such as Mumetal or the like, and where the apparatus can be switched offwhen the action on the operating sensor by the operator stops.

BACKGROUND OF THE INVENTION

A safety device of the type discussed is recommended for all types ofapparatus used by an operator, in order to protect the operator againstaccidents or to avoid unsupervised operation of the apparatus used bythe operator. A safety device of this type is recommended, for example,for a grinder, milling machine or the like, as well as for a water orfoam type fire extinguisher of a fire fighting device, an acetylenetorch, a spray head for paint work or metal die casting, etc. Such asafety device is of particular importance for a sandblasting device of asandblasting unit for pressure sandblasting--dry blasting, moistblasting, wet blasting--where such a safety device acting, so to speak,as a deadman's switch is required by safety regulations. Withoutintending to limit of the filed of application of a safety device of thetype discussed, this safety device is primarily explained below by meansof the example of a sandblasting device.

In a known safety device for an apparatus to be manipulated by anoperator (DE-U 86 13 771), particularly intended and usable for asandblasting device of a sandblasting unit, where the device to bemanipulated by the operator is connected via a supply line for a supplymeans, in this case compressed air, to a supply source, the operation ofthe device is controlled from the supply source. A control device isprovided on the supply means source, by means of which the input of thesupply means can be controlled. The control device is actuated by anoperating sensor disposed on a handgrip of the device. The operatingsensor is connected via a cable to the control device. When theactuation of the operating sensor by the operator ceases, the device isswitched off.

The operating sensor of the known safety device is designed as anelectronic proximity sensor, preferably operable contact-free, which ispreferably actuated by a special actuation element, particularly a foil.Besides the operating sensor the device is further provided with anormmal operating unit for remote operation of the device. This normaloperating unit has a plurality of activating elements for differingfunctions.

In the previously described known safety device there is furthermoreprovided a relief device for the supply line for the purposes ofswitching off the device as quickly as possible. This relief device isdisposed at a point in the supply line distant from the device near theconnection of the supply line to the supply means source. It has arelief cross section which approximately corresponds to the flow crosssection of the supply line. A shut-off device for the supply line isassociated with the relief device, the two devices being locked off fromeach other in terms of circuitry.

In the known safety device it is considerably more difficult to bypassthe operation sensor than, for example, the mechanical hand lever of adeadman's switch or the like. However, a bypass is not impossible.Finally, although in the known safety device the reverse relief of thesupply line, which is important for reasons of safey, is beneficial inits effects, it entails great expenditures for construction and theprevention of wear, especially if highly abrasive sandblasting means areused in a supply line.

SUMMARY OF THE INVENTION

It is an object of the invention to improve the known safety device suchthat a bypass of the operating sensor becomes for all practical purposesimpossible and that the supply line is optimally shut off upon sensorresponse.

This object is attained in a safety device for an apparatus used by anoperator according to the present invention in that the operating sensoror at least one indicator element of the operating sensor is disposed onthe hand of the operator, in particular that it has been integrated intoa protective glove for the hand of the operator. Because of the factthat the operating sensor is provided on the hand of the operator,bypassing of the safety device or of the operating sensor is totallyimpossible, since the device itself is only passive. Without theoperating sensor associated with the hand of the operator, operation ofthe device is systematically impossible.

Furthermore, the object described above is also attained from theviewpoint of safety by the characteristic that the supply line can becompressed at least in the area of the relief device and/or the shut-offdevice, and that the relief device and/or the shut-off device, or both,each have a movable compression element. The provision of the reliefdevice and/or the shut-off device as compression elements isparticularly simple and sturdy and results in an optimal adaptation tothe technical requirements even and especially with the use of highlyabrasive sandblasting means as supply means.

There are many ways to design the safety device according to theinvention in a practical manner and to improve it. This is illustratedby means of the drawings in connection with the ensuing description of apreferred exemplary embodiment of a sandblasting unit equipped with asafety device of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an exemplary embodiment of a sandblastingunit for compressed air blasting,

FIG. 2 is a schematic view of the area of a device of a sandblastingunit in accordance with claim 1, to be manipulated by an operator,

FIG. 3 is a detail of the sandblasting unit of FIG. 1 by way of exampleand in enlargement,

FIG. 4 a detail similar to FIG. 3 in another embodiment, and

FIGS. 5a-5d are views of the area of the sandblasting unit of FIG. 1shown in FIG. 4 in various functional states.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

It should be mentioned beforehand that, instead of the sandblasting unitfor compressed air blasting shown in FIG. 1, other devices may be used,for example a foam-type fire extinguishing unit as previously mentionedin the present description. The sandblasting unit shown in FIG. 1 has acompressed air line 1 connected to a supply means source 3, in this casein the form of a usual sandblasting supply container. From a connectorof the sandblasting supply container 3 a supply line 7 leads to a device8 which is manipulated by an operator 30. In the exemplary embodimentshown here the supply line 7 is a line for compressed air and blastingsand, and the apparatus 8 is a sand blaster or blast nozzle.

The sandblasting unit shown in FIG. 1 is provided with a safety device 9for the apparatus 8 which is manipulated by the operator having acontrol device 10 for controlling the operation of the apparatus 8 aswell as an operating sensor 12 provided on the apparatus 8 which isactuated by the operator and which is connected with the control device10 via a cable 11. The apparatus 8 can be switched off when the actionon the operating sensor 12 by the operator 30 stops.

As shown in FIG. 1 in combination with FIG. 2, the operating sensor 12is inconspicuously placed in the exemplary embodiment shown here. Thisis made possible by the operating sensor 12 being embodied as anelectronic proximity sensor which preferably can be actuatedcontact-free. In general such a proximity sensor can be actuatedinductively capacitively, optically, thermically or acoustically, andthis will be further explained below. Furthermore, reference is made tothe voluminous technical literature in connection with electronicproximity switches, preferably those actuable in a contact-free manner.

It is further suggested in FIG. 1 that beside the operating sensor 12 anormal actuating unit 15 for remote control of the apparatus 8 has beenprovided. Such a normal actuating unit 15 is used for the normaloperation of the apparatus 8 while the operating sensor 12 is used morefor emergency operation, particularly in connection with a deadman'sswitch. A normal actuation unit 15 can have normal operating elements,for example, for the functions of sandblasting means on/off, compressedair on/off, additives on/off, and so forth. FIG. 2 shows that such anormal actuating unit 15 can be disposed physically separate from theapparatus 8, on a belt worn by the operator 30.

FIGS. 1 and 2 further show that the apparatus 8 has a handgrip 17, whichis to be grasped or enfolded by the hand of the operator 30, and that anintercom 19 is provided here, in accordance with the preferredteachings. The normal actuating unit 15 on the belt of the operator 30serves simultaneously as a local central control unit and includes theintercom 19.

Finally it is suggested in FIG. 1 that at a location of the supply line7 remote from the apparatus 8, namely at a place close to the connectionof the supply line 7 with the supply means source 3, there is provided arelief device 21 for the supply line as well as, and also in accordancewith the preferred teaching, a shut-off device 22 for the supply line 7.The relief device has a relief cross section which approximatelycorresponds to the flow cross section of the supply line 7, so that aquick and effective relief in the reverse direction can take place. Inthe concretely shown exemplary embodiment the supply line 7 can, forexample, have a diameter of 42 mm, i.e. have a flow cross section ofapproximately 1,330 mm². The relief device 21 would then also have thisdiameter. In a supply line of 400 m length, relief only takes a fewseconds, clearly less than 5 sec. At the same time it can be assured bymeans of the shut-off device 22, with the locking of the relief device21 and the shut-off device 22 that is provided, that no further supplymeans will flow from the supply means source 3.

In the exemplary embodiment of a sandblasting unit shown in FIGS. 1 and2 as an example of such a unit in general, the operating sensor 12, heremore exactly an indicator element of the operating sensor 12, isdisposed on the hand of the operator 30. In the preferred exemplaryembodiment shown here the indicator element of the operating sensor 12has been integrated into a protective glove 32 for the hand of theoperator 30. In the exemplary embodiment particularly clearly shown inFIG. 2 the indicator element of the operating sensor 12 is an air coil33 which has been integrated here into the palm of the protective glove32. The air coil 33 is connected in the exemplary embodimemt shown herewith a central electronic device or electronic triggering device via aconnecting cable 34, which will be described in more detail below. Plugor button contacts are indicated in the area of the wrist of theprotective glove 32. In the preferred exemplary embodiment here shownthe air coil is distributed flat across the palm and up into the indexfinger and thumb of the protective glove 32. The main point is that itis particularly practical if the indicator element is disposed in thepalm of the protective glove 32 at a point maximally free of movement,particularly between thumb and index finger. However, the indicatorelement does not have to have the wide expanse concretely shown in FIG.2. This results in a further safety measure, namely that grasping theapparatus 8 with the bare hand does not result in actuating theoperating sensor 12, and thus the operator 30 is forced to wear theprotective glove 32 at work. This results in the advantage thatbypassing the operating sensor 12 and nullifying the safety effect ofthe safety device 9 of the invention is extremely difficult for theaverage operator 30. Since the operating sensor 12 is associated withthe protective glove 23, i.e. with the operator 30, bypassing the safetydevice 9 is impossible, simply because the apparatus 8 itself is onlypassive. If the operating sensor 12 and particularly its indicatorelement can only be activated by a special actuator element, then it issuggested to dispose the actuator element on the apparatus 8 in thepresent exemplary embodiment, and in particular to integrate it flatinto the surface of the apparatus 8. This has only been sketched in inFIG. 2. A point in particular is that, for example, the foil forming theactuator can be wound or glued around a nozzle, a nozzle holder or thesupply line 7 itself. Another point is that the actuator element can beintegrated, particularly by vulcanizing, into a rubber hose, forexample, which is attached to the apparatus 8 at a suitable spot. It isespecially recommended to integrate the actuator element into thehandgrip 17, preferably of course into the gripping surface of thehandgrip 17.

Previously it has already been briefly discussed that the electronic andpreferably contact-free operable proximity switch of the invention canbe operated as operating sensor by inductive, capacitive, optical,thermal or like means by the operator. Besides the embodiment as aninductive proximity switch previously thoroughly discussed, a number offurther embodiments are to be discussed which have not been shown in thedrawings.

First, it could be recommended to provide the operating sensor in theform of a capacitative proximity sensor. The hand of the operator couldthen, for example, cause the actuation of the response capacity of thecapacitative proximity sensor.

A further alternative is also to provide the operating sensor in theform of a magneto-elastically operating sensor. For example, themagneto-elastic effect of such a sensor could be utilized during thegrasping of a handgrip and the change of the mechanical load on aprotective glove of an operator connected therewith.

Similarly to a magneto-elastically operating sensor, a sensor operatingpiezo-electrically could be provided. In this case the mechanial workwould be translated into electric voltage.

In accordance with another alternative, the operating sensor could beprovided as a wire strain gauge sensor, particularly with a least onesemiconductor wire strain gauge. Such wire strain gauge sensors can becheaply and practically used, especially when using modern semiconductortechnology.

Of particular importance is a further teaching of the inventioncharacterized by providing the operating sensor as a sound sensor,preferably a structure-borne sound sensor, particularly astructure-borne sound microphone. Because of the susceptibility tointerference of a sound sensor reacting to sound transmitted through theair, a structure-borne sound sensor is provided here in a particularlypreferred way. Often a microphone specially tuned to structure-bornesound and structure-borne sound measurement is used. Such sensors areknown from the technical literature. The supply means exiting theapparatus, particularly the sandblasting material carried by airpressure in a sandblasting unit, generates high-frequency oscillationsin the apparatus, particularly in the nozzle body of the sandblastingunit. Now if, for example, a structure-borne sound microphone has beenintegrated into a work glove of an operator and is connected to thecontrol device, this structure-borne sound microphone registers thestructure-borne sound in the nozzle body whenever, and only whenever,the work glove tightly surrounds the handgrip of the nozzle body. Thistechnique makes it unnecessary to adapt the apparatus itself in anymanner.

The only possible way to circumvent the operating sensor describedabove, in particular a structure-borne sound sensor, is to impose on itthe structure-borne sound frequencies occurring in the operation of theapparatus itself. In order to provide a special level of protectionagainst outside influence here, it is recommended that the controldevice have at least one frequency filter associated with the soundsensor. A frequency filter in the control device can be embodied, forexample, as either a low-pass, high-pass or band-pass filter. It is alsopossible to connect several frequenccy filters in parallel in order toselectively determine different frequencies normally occurring duringoperation of the apparatus. Specific frequencies can also be filteredout with such frequency filters (set-point sound).

In the previously discussed safety installation and sound sensor, notonly is there a determination whether the operator is actually actuatingthe operating sensor, but it is determined at the same time whether ornot the apparatus is operating. Although this is advantageous, it meansa special provision must be made during the start-up of the apparatus,when there is no sound or structure-borne sound yet. In this case it isrecommended that the control device be provided with a bypassing switchand that it be possible to bypass while the apparatus to be manipulatedby the operator is starting up, until the corresponding set-point soundoccurs. It can be provided in the design of the circuit that thebypassing switch in the control device is automatically opened as soonas a set-point signal, indicating actuation by the operator and theoperation of the apparatus, has been generated.

It has not been shown in the drawings that a delay switch can beassociated with the operating sensor if this is considered practicalgiven the circumstances of use. Also not shown in the drawings is thatthe operating sensor, as already mentioned, can be provided in the formof a proximity sensor only actuated by a special actuator element,particularly a foil, preferably of aluminum, copper, a material of lowmagnetic retentivity with high initial permeability, such as Mumetal orthe like. Mumetal or materials with high initial permeability as theyare known, for example, for use in magnetic screens, are suitable to aparticular degree, since in this way metals such as steel, aluminum,zinc, copper or the like cannot interfere with the operating sensor.Accidental interference can therefore by safely prevented.

Finally, FIG. 2 shows that in the exemplary embodiment shown therein theelectronic control associated with the indicator element of theoperating sensor 12 can be integrated into the normal actuating unit 15.Furthermore, FIG. 2 also shows that the intercom 19 is connected via acable 35 with the normal actuating unit 15.

Special attention is required for the connection via a cable 11 of thecontrol device 10 to the apparatus 8 or to the operator 30. The cable 11can be divided, one part carrying the current supply for the operator 30and the other part transmitting the signals. Of course, by use of thecorresponding filter techniques, single cables 11 can also be used. Aparticular problems lies in protecting the cable 11 against damage. Inthis respect FIG. 2 in combination with FIG. 1 shows a particularlypreferred exemplary embodiment in that in this case a a ventilating airline 36 has been provided between the supply means source 3, or pressuregenerator, and the operator 30 and the cable 11 for the connection ofthe control device 10 with the apparatus 8 is disposed on the inside ofthe ventilating air line 36. This integration of the cable 11 and theventilating air line 36, required in any case for protecting thebreathing of the operator 30, guarantees a particularly protected way tobring the cable 11 to the operator 30. If a ventilating air line 36 perse is not present, the cable 11 can, of course, be integrated with otherlines present, for example the supply line 7 or, more practically withan auxiliary air line perhaps extending parallel to the supply line 7.As far as the following explanation of the integration into theventilating air line 36 is concerned, this is also correspondingly truefor the integration into other lines.

In the exemplary embodiment explained above, naturally the ventilatingair line 36 should have a cable connector 37 or cable lead-in thevicinity of the control device 10 and in the vicinity of the apparatus8, respectively. Such a cable connector 37 can be in the form of aplug-in connection in a plurality of different ways. If embodied as acable duct or cable lead-in, a discrete connecting element is notnecessary. However, sealing of the led-in or ducted cable 11 is thenrequired. In general, the state of the art should be considered inrespect to the construction of such connectors or lead-ins.

FIG. 1 shows a particular layout, in that here the ventilating air line36, or any other line, comprises separate line segments 39 which can beconnected by means of connecting elements 38, the connecting elements 38at the same time serving as pneumatic connections of the line segments39 and as the electrical connection of individual cable segments of thecable 11. FIG. 4 shows this schematically for two line segments 39.

As far as the relief device 21 and the shut-off device 22 are concerned,FIG. 1 shows these only schematically as shut-off elements. Suchshut-off elements are in the form of ball-cock valves, slide valves, orthe like.

However, FIGS. 3, 4 and 5a-5d show particularly preferred embodiments ofa relief device 21 for the supply line 7, and of a shut-off device 22,which are particularly simple and sturdy. The exemplary embodimentsshown here require that the supply line 7 is compressible, at least inthe area of the relief device 21 and/or the shut-off device 22. This istrue for the supply line 7 itself as well as for relief connector 50brought through the relief device 21. It is important in all cases thatthe relief device 21 and/or the shut-off device 22, or both, each haveone movable compression element 51 for compressing the correspondingsupply line 7 or the relief connector 50. In the preferred exemplaryembodiment here shown, the compression element 51 can be moved by apneumatic or hydraulic drive, particularly by a bellows cylinder 52.

The preferred embodiment shown in FIG. 3 has a supply line 7 and arelief connector 50 extending side by side and parallel to each other. Acompression element 51 is disposed between the supply line 7 and therelief connector 50 in a housinng 53, surrounding the relief device 21,the shut-off device 22, the supply line 7 in this area, the reliefconnector 50 in this area and the compression element 51. By means ofthe propulsion by the bellows cylinder 52 shown here, which is actuablepneumatically, i.e. via a control pressure line 54, the compressionelement 51 of FIG. 3 can either be moved downward for opening the supplyline 7 and closing the relief connector 50, or upwards for relief, i.e.the opening of the relief connector 50 and the closing of the supplyline 7. The drive thus works in two directions. This is attained in thepreferred exemplary embodiment shown here by the provision, inopposition to the direction of action of the bellows cylinder 52, of aspring 55 embodied as a helical pressure spring, which normally tries tocompress the bellows cylinder 52 and moves the compression element 51 inthe device here shown in the direction of the state of relief. Thesupply line 7 is therefore open and the relief connector 50 closed onlywhen the bellows cylinder 52 is under pressure, if the control pressurefalls off, the spring 55 upwardly compresses the bellows cylinder ofFIG. 3 and in this way compresses the supply line 7.

FIG. 1 shows in connection with the above explanation that the controlpressure line 54 for the relief device 21 and the shut-off device 22 canbe readily connected to a common compressed air generator, with which,for example, the compressed air line 1 associated with the supply meanssource 3 is also connected. For the purpose of controlling the bellowscylinder 52, FIG. 3 additionally shows a control valve 56 on the controlpressure line 54 which, in the exemplary embodiment shown here, can beprovided as a simple 3/2-way valve.

The further exemplary embodiment of the teachings previously explainedin principle shown in FIGS. 4 and 5a-5d, first also has a compressionelement 51 and a bellows cylinder 52 as a pneumatic drive. Thisexemplary embodiment, described by means of FIG. 4 for the shut-offdevice 22 of the supply line 7 is distinguished by great simplicity andexcellent retrofitting ability for existing supply lines 7. The housing53 is here made in the shape of a box with lateral walls and front andback walls, the front and back walls each having approximately U-shapedrecesses on their upper edges for receiving the supply line 7. Thesupply line 7 can be inserted from above into these recesses 57. Asshown by FIG. 4, the housing 53 is then closed by a sliding lid 58 whichin the inserted state is prevented by holding flanges on the housing 53from upwardly lifting off the housing 53. With the compression element51 on the bellows cylinder 52, which here is provided as a compressionstrip extending crosswise to the supply line 7, is associated acorresponding compression element 59 on the inside of the lid 58. Ifduring operation and with the supply line 7 inserted compressed air isfed via the control pressure line 54, also present here, to the bellowscylinder 52, the later expands, lifts the compression element 51upwardly and thus compresses the supply line 7 between the compressionelements 51 and 59. Furthermore, a pressure relief line 60 for thebellows cylinder 52 is also shown. A control valve, not shown, forexample a 4/2-way control valve, can be connected to the lines 54, 60.

In a clearly comprehensible way the cooperation of a relief device 21and a shut-off device 22, both constructed in accordance with the systemof FIG. 4, is shown in FIGS. 5a-5d. The two bellows cylinders 52 whichin the exemplary embodiment shown here constitute the drive for thecompression elements 51, are connected to each other and to a controlpressure line, not shown, via a control valve 56, here embodied as a5/2-way valve, such that in case of a 1/0 signal, one of the two bellowscylinders 52 is always extended and the other of the two bellowscylinders 52 is always compressed. FIGS. 5a and 5c show the normaloperating condition with the supply line 7 open and the relief connector50 compressed, the direction of flow being shown at the lower left ofFIG. 5. FIGS. 5b and 5d 5 the relief position is shown with the supplyline 7 compressed and the relief connector 50 open, the directions offlow again in the lower right. This technology is especially practicaland an existing system can be retrofitted easily. The design of thedrives in the form of bellows cylinders 52 is sturdy and requires littlemaintenance, especially since the bellows cylinders 52 are protectedagainst damage by the housing 53 in the present exemplary embodiment.The pneumatic control from the source of compressed air via the controlpressure line is typical for the system and thus is particularlypractical.

It is to be understood that the description of the exemplary embodimentshas been given by way of example only and that further improvements andvariants are possible within the scope of the invention.

What is claimed is:
 1. A safety device for an apparatus connected to apower supply via a supply line, said apparatus to be used by anoperator, said apparatus comprising:a handgrip grasped by the operator;a power source controlling the operation of the apparatus; a controldevice for control of the operation of the apparatus; an electronicoperating sensor disposed on the apparatus and having one electronicsensing element; said operating sensor actuated by the operator; saidoperating sensor being actuated by an actuating element, this actuatingelement being completely separate from said operating sensor; saidapparatus being switched off when the operator's action on the operatingsensor stops; at least said electronic sensing element of said operatingsensor being disposed on the hand of the operator; and said actuatingelement being the handgrip as such or some special element disposed onsaid handgrip, particularly a foil forming said actuating elementpositioned on said handgrip.
 2. The safety device acccording to claim 1wherein said operating sensor or, at least, said electronic sensingelement is integrated into a protective glove for the hand of theoperator.
 3. The safety device according to claim 2 wherein an inductionloop is integrated into the palm of the protective glove.
 4. The safetydevice according to claim 2 wherein an air coil is integrated into thepalm of the protective glove.
 5. The safety device according to claim 2wherein at least said electronic sensing element in the palm of theprotective glove is disposed at a location as free as possible ofmovement.
 6. The safety device according to claim 5 wherein saidoperating sensor or said electronic sensing element is disposed betweenthe thumb and index finger of the glove.
 7. The safety device accordingto claim 1 wherein the actuating element is disposed on the apparatusand integrated flat into the surface of the apparatus.
 8. The safetydevice according to claim 7 wherein the actuating element is integratedinto the handgrip.
 9. The safety device according to claim 8 wherein theactuating element is integrated into the gripping surface of thehandgrip.
 10. The safety device according to claim 1 wherein saidoperating sensor is a sound sensor.
 11. The safety device according toclaim 10 wherein said sound sensor is a structure-borne soundmicrophone.
 12. The safety device according to claim 11 wherein thecontrol device has at least one frequency filter associated with thestructure-borne sound microphone.
 13. The safety device according toclaim 10 wherein the control device is equipped with a bypassing switchpermitting the operating sensor to be bypassed during startup of theapparatus.
 14. A safety device for an apparatus connected to a powersupply via supply line, said apparatus to be used by an operator, saidapparatus comprising:a handgrip grasped by the operator; a power sourcecontrolling the operation of said apparatus; a control device forcontrol of the operation of the apparatus; wherein at a position in thesupply line in the vicinity of the connection of the supply line to thepower supply a relief device for the supply line is provided; saidrelief device for the supply line having a relief cross sectionapproximately corresponding to a flow cross section of the supply line;and a shut-off device for the supply line is associated with the reliefdevice for the supply line; the relief device and the shut-off devicebeing blocked in relation to each other; wherein the supply line iscompressible at least in the relief device and at least the reliefdevice has a movable compression element.
 15. The safety deviceaccording to claim 14 wherein the compression element is movable bymeans of a pneumatic or hydraulic drive.
 16. The safety device accordingto claim 15 wherein the compression element is movable by means of abellows cylinder.
 17. The safety device in accordance with claim 1wherein said actuating element disposed on said handgrip is a foil whichforms the actuating element.